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Help! My coil almost works

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LAN_403

Seoul_lasers

Sat Aug 23 2008, 05:28PM

Registered Member #1630 Joined: Sat Aug 09 2008, 11:36AM
Location: Seoul Korea
Posts: 115

Firefox wrote ...

Could it be that the topload is too big and the capacitance prevents breakout at that power level?

Well, ok.. that could be true but often I find that if the topload is too big you'll get racing sparks down the side of your secondary.
It has happened always for my coils.

--Sorry to hear that the coil is still not working. Can you send me a picture of the set up, then maybe I can give you some pointers.

Ultra7

Sat Aug 23 2008, 05:39PM

Registered Member #1157 Joined: Thu Dec 06 2007, 12:11PM
Location: Houston, TX
Posts: 307

Zorink wrote ...

I've been looking around the forums and I found some things about the RF ground not being wired correctly. Here is how mine is hooked up - is it ok?

The Safety gap side of the Terry Filter goes to the NST ground, and the RF Ground side of the Terry Filter goes to . . .RF ground.
I Have a pic around here somewhere, I'll attach it when I find it.

Here we go with my MAD Paint Skills!

Seoul_lasers

Sat Aug 23 2008, 06:06PM

Registered Member #1630 Joined: Sat Aug 09 2008, 11:36AM
Location: Seoul Korea
Posts: 115

Huh, delete this please. forum is double tapping.

Seoul_lasers

Sat Aug 23 2008, 06:08PM

Registered Member #1630 Joined: Sat Aug 09 2008, 11:36AM
Location: Seoul Korea
Posts: 115

Ok, I was going to send you a PM.. but hmm
forum is acting slow right now.

Ok, I see 3 problems in the pictures.

1) I think your secondary is too far above the primary. For performance lower the secondary to that it either meets or is just slightly above the primary (1cm), otherwise your secondary isn't sitting the magnetic field and can't get the power it needs to resonate properly.
( don't over couple the secondary by lowering it too much or you will have racing arcs on the secondary coil) that will do damage!
2) GET RID of the terry filter. run the coil without it for right now.
the power you are running really doesn't require you to have one.
I started using them when I was running 12Kv-+120mA supplies. I also omitted the MOVs as they are also not really needed.
A safety spark gap 0- 0 -0 and a 30Kvdc ~500pF (capacitance really doesn't matter) rated ceramic filter cap is pretty much what is going to save your transformer.

3) TAKE the strike rail off. THAT is a MUST !!!

Estragon

Sat Aug 23 2008, 08:10PM

Registered Member #1391 Joined: Fri Mar 14 2008, 04:49PM
Location:
Posts: 40

Sorry, OT. But maybe it is a related problem.
I also have troubles with my coil. Alothough it is an entirely diffrent 'design'. But, my scondary coil is placed an inch bellow the primay, is this what may cause the problems? Are the bottoms of the coil supposed to be alligned?

Zorink

Sat Aug 23 2008, 10:07PM

Registered Member #1292 Joined: Wed Feb 06 2008, 04:09AM
Location: Mesa, AZ
Posts: 25

@Cain: That's close to how I set mine up. Here's a pic

@Mods: Sorry for being a n00b

I fixed it and linked to my RF instead of posting the large image.

@lasers: I don't have any racing sparks. Also, take the strike rail off and get rid of the filter? I thought they were needed for safety? I'll move the primary up a bit and see how that works.

@Ultra: Mine was wired incorrectly, could that cause the bad performance? I'll hook it up according to you mad diagram skillz this time.

Kristian

Sat Aug 23 2008, 10:44PM

Registered Member #611 Joined: Wed Mar 28 2007, 11:40PM
Location: Hudsonville, Michigan
Posts: 79

Zorink,

I think I know whats going on here, and it is a two, possibly three part problem.

1. Your coils might not be coupled tight enough. If this is the case, most of your primary capacitors energy isn't transferring to the secondary and is instead getting eaten by the spark gap.

2. Your gap might not be quenching. Force some air through that puppy. I use a vacuum cleaner motor on my "RQ" style gap. You could probably use your single gap with some forced air from an air compressor or just hook a shop vac hose to it. If it isn't quenching, it's just eating up the power.

3. Your tuning is off (possibly). You have to do this manually. There is no other way to get it accurate. This is where I would start. If your tuning is bad, it will be difficult to trouble shoot anything else. Move that tap around and see what happens. Try to find the point on your primary that produces the longest arcs from your topload. It doesn't matter if this doesn't increase the arcs to monster lengths, it's just to be sure that the coils are in tune. Then start messing with the coupling and the gap.

Everything else looks great, man. Nice job on the construction. Your grounds are fine. I personally put the nst and rfi filter on my mains ground, but it doesn't make a difference. The top load looks a little on the small side, but it isn't anything to be concerned with. Leave the strike rail and the Terry filter. Check the three things I mentioned, and if none of those things are the problem, then start looking at the filter.

Estragon,

You need to consider the coupling coefficient of the coils. It's not so much if the coils are even with each other or if the secondary is up or down from the primary, but how much of the primary's magnetic field is "felt" by the secondary. If the coupling is too low, you should lower the secondary. If the coupling is too high, you raise the secondary.

I usually start with 1.25" clearance between the inner turn of the primary and the secondary with the bottom turn of the secondary even with the inner turn of the primary. I then input the specs of my coil into Javatc, and adjust the hight of the secondary in the program until I reach the desired coupling value.

Here's some info on coupling,

Here's a link to Javatc,

Zorink

Sun Aug 24 2008, 12:34AM

Registered Member #1292 Joined: Wed Feb 06 2008, 04:09AM
Location: Mesa, AZ
Posts: 25

@Kristian: Thanks for the java app. It recommended that I raise My primary by 1.25 inches. I'll try that and then tweak the tuning some more.

Coronafix

Sun Aug 24 2008, 01:43AM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Lower secondary (raise primary)
adjust tuning manually.
Leave the rest, it looks great, I don't use a Terry filter at all but I wouldn't advise against it.
Once it's tuned, you'll see why the strike rail is needed.

Seoul_lasers

Sun Aug 24 2008, 03:07AM

Registered Member #1630 Joined: Sat Aug 09 2008, 11:36AM
Location: Seoul Korea
Posts: 115

Coronafix wrote ...

Lower secondary (raise primary)
adjust tuning manually.
Leave the rest, it looks great, I don't use a Terry filter at all but I wouldn't advise against it.
Once it's tuned, you'll see why the strike rail is needed.

A terry filter can be done without using MOVs ... simply 2 100 ohm resistors 30Kvdc worth of ceramic capacitors ( I use 500pF) and a 3 some gap O- O -O . it works very very well. FORGET MOVs!!

Strike rail is NOT needed running 370W of power to your coil. 1) Your sparks won't be big enough.. 2 the modded terry filter will provide ample protection to the xmfrs. Like I said I have been using the same xmfrs for 2 years, I have taken countless strikes to the primary. NO problems at all.

-- btw, I did the measurement on your secondary , I am 99% sure your coupling is off now. make the secondary flush with to top of your primary windings. that is the problem I am sure of it now.

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